Yep, K-plan got it spot on.
Its basically a function script, that allows us to keep a visual style and colours, across all DietPi scripts.
Because bash scripts can’t talk to each other (No class support, like C++), instead of us coding in the colours and styles in each script, we just call the notify script and it does it all for us.
Some examples:
root@DietPi:~# /DietPi/dietpi/func/dietpi-notify 0 sucess
[Ok] sucess
root@DietPi:~# /DietPi/dietpi/func/dietpi-notify 1 failure
[Failed] failure
root@DietPi:~# /DietPi/dietpi/func/dietpi-notify 2 info
[Info] info
root@DietPi:~# /DietPi/dietpi/func/dietpi-notify 3 DietPi-Program_Name Doingsomething
DietPi-Program_Name
─────────────────────────────────────────────────────
Mode: Doingsomething
Please wait...